Preventing media misalignment during accumulation

ABSTRACT

In one example in accordance with the present disclosure a system for preventing media misalignment during accumulation. The system includes a number of media clamps having multiple positions to prevent misalignment of an incoming media sheet during accumulation. The number of media clamps are in a raised position after a leading edge of the incoming media sheet has passed over a trailing edge of the stack region. The media clamps are in a clamped position after the leading edge of the incoming media sheet has passed the media clamp.

BACKGROUND

Printing systems are used to deposit printing fluid such as ink, onto a print medium such as paper. After the print medium has been printed on, additional operations such as stapling, collating, offsetting a stack, and other post-printing operations may be performed on a stack of printed media.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various examples of the principles described herein and are a part of the specification. The illustrated examples are given merely for illustration, and do not limit the scope of the claims.

FIGS. 1A-1C are examples of a system for preventing media misalignment during accumulation, according to one example of the principles described herein.

FIG. 2 is a flowchart of a method for preventing media misalignment during accumulation, according to one example of the principles described herein.

FIG. 3 is a top view of a system for preventing media misalignment during accumulation, according to another example of the principles described herein.

FIG. 4 is a side view of the system of FIG. 3, according to one example of the principles described herein.

FIG. 5 is a flowchart of a method for preventing media misalignment during accumulation, according to another example of the principles described herein.

FIG. 6 is a side view of a media clamp for preventing media misalignment during accumulation, according to one example of the principles described herein.

FIGS. 7A-7E are diagrams of the method for calibrating a media clamp, according to one example of the principles described herein.

FIG. 8 is a diagram of a media clamp, according to another example of the principles described herein.

Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.

DETAILED DESCRIPTION

As described above, printing systems are used to deposit a printing fluid such as ink, onto a print medium such as paper. Other examples of print fluids include three-dimensional print agents, bio-fluids, pharmaceutical agents, etc. Other examples of print medium include three-dimensional printing medium such as powder. After a printing system has deposited the ink onto the print medium, a finishing system that may be separate from, or integral with, the printing system executes finishing operations such as, but not limited to, aligning the stack, offsetting the media sheets, and stapling the media sheets together. While these finishing systems are useful at performing such operations, they are less efficient in some scenarios.

For example, during finishing operations, it is desirable for both the long and short edges of the media to be well-aligned to accommodate those finishing operations. Accordingly, a finishing system, which again may be separate from or integral with a printing system, should have sufficient control over a media sheet to be able to move the media sheet along multiple axes to align the edges and to maintain this alignment for subsequent operations. Such operations are difficult and become even more difficult when working with certain media, such as undried or partially-dried media.

For example, media with undried or partially-dried printing fluid may distort due to the expansion of fibers in the media. The expansion of these fibers causes curl and cockle in the print medium. Also, the presence of a printing fluid reduces the beam strength, i.e., the stiffness, of the media sheet such that it has a higher tendency to buckle under an applied force. Still further, as ink is deposited on the surface of the media sheet, the expansion of the paper fibers on the surface changes the surface properties which increases the surface frictional properties of the media sheet. Each of these conditions complicates the handling of media sheets that have been printed on with a printing fluid.

One specific complication is sheet curl that results as a sheet distorts due to the application of a printing fluid. If a previously printed sheet in a media stack has enough curl, an incoming media sheet may interact with the previously printed sheet and pull the sheet in the stack over on itself. Still further, if an incoming sheet collides with a previously printed sheet, the force of collision may pull the incoming media sheet out of a media transport device to result in either a moderate or significant misalignment of the incoming sheet. The misalignment in some cases causes a paper jam. If the trailing edge curl of the previously printed sheet is not so severe that collision with by an incoming sheet grossly misaligns the incoming media sheet, there still may be sufficient force on the incoming media sheet such that an x- and y-alignment as well as a z-axis rotation of the incoming media sheet is impacted; which again may result in a paper jam, or may have some other negative impact on job quality.

Yet another complication is that curled media sheets do not lay flat when stacked and thus create air cushions between sheets in a stack. This trapped air cushion lowers the sheet-to-sheet friction such that media sheets slide more easily relative to one another, impacting the ability to maintain stack alignment. The air cushions also increase the stack height reducing the capacity of the media support device.

Yet another complication is the alignment of incoming media sheets. For example, in some devices, a y-alignment, or an alignment along a transport direction of the media is performed by an alignment wall. As a media transport device releases the incoming media sheet, kinetic energy in the media sheet may cause the sheet to bounce off the alignment wall, pushing the media sheet away from the alignment wall. Such a pushing away may result in a misalignment in that direction or even a curl of the media sheet near the alignment wall.

Finishing systems have been devised to address incoming media sheet alignment. For example, in some finishing systems an incoming media sheet is ejected onto a previously accumulated stack. Before and during the ejection, the device may use a tapping action on two parallel edges of the media sheet to move the media sheet into the desired position and alignment in a single direction. Before or after this first alignment, a second operation is carried out to align the stack/sheet in a second direction. While this process may work for relatively flat media, it does not address the complications mentioned above that arise when dealing with an undried or partially-dried, and therefore non-flat, media. In other words, the present systems do not account for the effects of page curl, i.e., undried or partially-dried media, nor do they accommodate alignment of the undried or partially-dried media, which undried or partially-dried media have characteristics that do not lend well to the alignment described above. In fact, some finishing systems, rather than executing finishing operations on undried or partially-dried printing media, first dry the media and then perform the finishing operations. However, such drying equipment is costly and further lengthens the time to output of a job.

The present specification describes a system and method for preventing media misalignment during accumulation, particularly an undried or partially-dried media. Specifically, the present specification describes a device and method for controlling and maintaining an x-direction alignment and a y-direction alignment of a sheet printed by a fluid printing system. Doing so simplifies post-printing value-added operations such as stack alignment, stapling, offset, and other finishing operations. The systems and methods described herein also control edge curl so as to not impact the transport of an incoming media sheet in the finishing system.

The system includes a number of media clamps having multiple positions to prevent misalignment of an incoming media sheet during accumulation. The media clamps are in a raised position after a leading edge of an incoming media sheet has passed over the trailing edge of the stack region. The media clamps are then returned to an intermediate or a clamped position after the leading edge of the incoming media sheet has passed the media clamp to maintain control of the incoming media sheet.

The present specification also describes a method for preventing media misalignment of an incoming media sheet during accumulation. The method includes placing media clamps having multiple positions in a clamped position until a leading edge of an incoming media sheet has passed over a trailing edge of a stack region. The media clamps are then raised after a leading edge of the incoming media sheet has passed over a trailing edge of a stack region and then lowered after the leading edge of the incoming media sheet has passed the media clamp.

The present specification also describes a system for preventing media misalignment of an incoming media sheet during accumulation. The system includes a number of sets of media clamps having multiple positions. Each set of media clamps corresponds to a different media size and/or orientation and maintains alignment of an incoming media sheet when the incoming media sheet is of a corresponding size. When maintaining the alignment, a set of media clamps 1) are in a clamped position until a leading edge of the incoming media sheet has passed over a stack region of a media support device, 2) are in a raised position after the leading edge of the incoming media sheet has passed over a trailing edge of the stack region, 3) move to an intermediate position after the leading edge of the incoming sheet has passed by the media clamp and 4) return to the clamped position either before or during the secondary alignment process (y-alignment). The set of media clamps are in a raised position when an incoming media sheet is not of a corresponding media size.

Certain examples of the present disclosure are directed to systems and methods for preventing misalignment of an incoming media sheet that 1) prevents page jams; 2) prevents page defects such as bent or rolled edges or corners: 3) accommodates finishing for undried or partially-dried incoming media sheets; 4) maintains page alignment in a media support device; 5) simplifies post-printing operations; and 6) addresses page curl and cockle as well as alignment for a variety of media sizes. However, it is contemplated that the devices and methods disclosed herein may prove useful in addressing other deficiencies in a number of technical areas. Therefore the systems and devices disclosed herein should not be construed as addressing just the particular elements or deficiencies discussed herein.

As used in the present specification and in the appended claims, the term “stack region” refers to a portion of a media support device defined by where the media is to be accumulated. For example, the stack region may be a sheet sized portion of a media support device. The stack region may correspond to the page size for a particular print media.

Further, as used in the present specification and in the appended claims, a “y-direction” refers to a transport direction of the incoming media sheet. While specific reference is made to the y-direction, any direction may be implemented as a y-direction.

Still further, as used in the present specification and in the appended claims, an “x-direction,” “x axis,” or similar terminology refers to a direction or axis that is perpendicular to the y-direction or y-axis. The x-direction, y-direction, and a z-direction as well, are indicated in multiple figures.

Even further, as used in the present specification and in the appended claims, the term “raised position” refers to any number of positions that are not a clamped position. Within a raised position is any number of sub-positions. For example, an intermediate position is an example of a raised position as is a high position.

Yet further, as used in the present specification and in the appended claims, the term “a number of” or similar language is meant to be understood broadly as any positive number including 1 to infinity; zero not being a number, but the absence of a number.

In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present systems and methods. However, the present apparatus, systems, and methods may be practiced without these specific details. Reference in the specification to “an example” or similar language indicates that a particular feature, structure, or characteristic described in connection with that example is included as described, but may not be included in other examples.

FIGS. 1A-1C are examples of a system (100) for preventing misalignment of an incoming media sheet (102), according to one example of the principles described herein. The system (100) includes a number of media clamps (104) having multiple positions to prevent misalignment of an incoming media sheet (102) during accumulation. As used in the present specification and in the appended claims, the media sheet (102) may be any type of suitable sheet or roll material, such as paper, card stock, transparencies, polyester, plywood, foam board, fabric, canvas, and the like. In another example, the print medium may be an edible substrate. Still further, in some examples, the media sheet (102) is an undried or partially-dry media sheet (102) meaning that the printing fluid on the print media (102) may still be wet, but may be dry enough so as to not smear or smudge. As described above, the systems (100) and methods described herein allow for efficient and effective handling of such partially-dry media sheets (102) where other finishing systems are not capable of so doing.

In the examples depicted in FIGS. 1A-1C an existing stack (106) of media is present. The size and shape of the stack (106) of media defines a stack region (114) of the media transport device. For example, the size of the media sheets in the stack (106) may define the stack region (114) that is used as a point of reference to determine when to raise and lower the media clamps (104). In other words, the stack region (114) is the region of a media support assembly that does or does not include an existing stack (106) and is the size of the incoming media sheet (102). Accordingly, the stack region (106) is dependent upon the incoming media sheet (102) size and each media sheet size has a corresponding stack region (114). As used in the present specification and in the appended claims, the trailing edge (108) of the stack (106), or more specifically the stack region (114), is the distal portion of the stack (106) or stack region (114) with respect to the sheet transport direction (112). The trailing edge (108) of the stack region (114) is the first part of the stack region (114) that an incoming sheet (102) interacts with. While the figures describe the incoming media sheet (102) as being added to an existing stack (106), in some examples, the incoming media sheet (102) may be the first sheet of a stack (106). In this example, the system (100) works similarly to how it would if there is an existing stack (106).

As depicted in FIGS. 1A-1C, the incoming media sheet (102) may be transported to be deposited on an existing stack (106) in a sheet transport direction (112). In the present specification, the sheet transport direction (112) may be a y-direction as indicated in the coordinate graphic. While the present specification describes the sheet transport direction (112) as a y-direction, the sheet transport direction (112) may be any direction. For the present specification, the directions noted are based on the coordinate system; however, other coordinate systems may be used.

The system (100) includes a number of media clamps (104), one of which is indicated in FIG. 1A. The media clamps (104) are devices that work to provide a clear path for an incoming sheet of media (102) and that control page curl within the stack (106) of media. The media clamps (104) function to compress the trailing edge (108) of a stack (106) of media sheets against a media support device. For example, as described above, sheets of the stack (106) may exhibit page curl due to the effects of deposition of a printing fluid as described above. Unchecked page curl (110-1) may impact the reception of an incoming media sheet (102). While the figures of the present specification illustrate curl (110) in a particular direction, i.e., an upward curl (110), the curl (110) can be in any direction, such as a downward curl.

As can be seen in FIG. 1A, an incoming media sheet (102) fed in sheet transport direction (112) may collide with a previously printed sheet having unchecked page curl (110-1). This collision of the incoming media sheet (102) with the sheet exhibiting page curl (110-1) may cause the page curl to roll over onto itself causing a defect identified as roll over. An example of page roll over is depicted in FIG. 1B. Page roll over may impact the subsequent receipt of incoming media sheets (102) and may affect the quality of the print job on the sheet with the unchecked page curl (110-1). Still further, the unchecked page curl (110-1) may cause misalignment of the incoming media sheet (102) by either partially or fully removing the incoming media sheet (102) from a media transport assembly that is positioning the incoming media sheet over the stack (106). Such removal from the media transport assembly may result in a misalignment of the incoming media sheet (102) which could cause a paper jam in the corresponding device.

To prevent this misalignment due to page curl, the media clamp (104) may be in a clamped position until a leading edge of the incoming media sheet (102) has passed over the trailing edge (108) of the stack region (114). Doing so may reduce the page curl. In other words, media clamps (104) generate a reduced page curl (110-2) in a sheet of the stack (106). A reduced page curl (110-2) has less, if any, impact on the incoming media sheet (102) as the media sheet with the reduced page curl (110-2) has been moved out of the transport path of the incoming media sheet (102). The media clamps (104) also serve to compress the stack (106), removing extraneous air cushions between sheets of the stack (106) reducing the propensity for misalignment of the stack (106).

While FIG. 1A depicts the media clamps (104) as being proximate to the trailing edge (108) of the stack region (114), the media clamps may be at other positions. For example, as depicted in FIG. 8, the media clamps (104) may be positioned at the trailing edge (108) so as to exert pressure on the corners of the stack (106). Still further, the media clamps (104) or additional media clamps (104) may be positioned at various points along the sheet transport direction (112) or other direction to accommodate curl or cockle in other portions of an incoming media sheet (102) and to further ensure proper alignment of the stack (106).

After, the incoming media sheet (102) has passed over the trailing edge (108) of the stack region (114), the media clamps (104) are moved to a raised position as depicted in FIG. 1B. As can be seen in FIG. 1B, and unchecked page curl (110-1) can roll over on itself due to frictional forces between the sheet with the unchecked page curl (110-1) and the incoming media sheet (102). However, due to the media clamp (104) previously being in a clamped position as indicated in FIG. 1A, the incoming media sheet (102) can pass over the reduced page curl (110-2) uninterrupted such that an incoming media sheet (102) can pass across the stack (106) without any complication. In the raised position, the media clamps (104) do not interfere with the transport of the incoming media sheet (102) over the stack (106). While FIG. 1B indicates the movement of the media clamps (104) between the clamped and raised positions as a pivot motion, the media clamps (104) may be raised and lowered via any form of movement such as vertical translation in a z-direction, or rotation in an x-direction. As the media clamps (104) move, the system (100) also includes a component for moving the media clamps (104). In some examples, this may be a motor that is coupled to a media clamp (104). In other examples, the movement of a media transport assembly may cause the media clamps (104) to raise and lower.

At some point after the alignment of the incoming media sheet (102), the media clamps (104) are returned to the clamped position as indicated in FIG. 1A to maintain an alignment, and control, of the incoming media sheet (102). For example at some point after the leading edge of the incoming media sheet (102) has passed the media clamp (104) in the sheet transport direction (FIG. 1A, 112) and after an x-direction alignment, the media clamps (104) are returned to the clamped position in preparation for another sheet reception cycle. In other words, the media clamps (104) cycle between a clamped position and a raised position as each incoming media sheet (102) of a job is received. Accordingly, for a printing device that prints at a rate of 40 pages per minute, the media clamps (104) may follow this cycle of raising and clamping 40 times in a minute.

While FIGS. 1A and 1B exhibit two positions, a clamped position and one raised position, a media clamp (104) may move between multiple raised positions. For example, as depicted in FIG. 1B, after the leading edge of the incoming media sheet (102) has passed over the trailing edge (108) of the stack region, the media clamps may be in a first raised position, i.e., a high position. Once the leading edge of the incoming media sheet (102) has passed beyond the media clamp (104) in a sheet transport direction (FIG. 1A, 112), the media clamp (104) may be placed in a second raised position, i.e., lowered to an intermediate position as indicated in FIG. 1C. The intermediate position may be raised above the media stack (106) by a distance that is less than the high raised position. For example in the intermediate position, the media clamps (104) may be between 5 and 7 millimeters above the stack (106). In this intermediate position, the media clamps (104) exert a reduced amount of pressure on the stack (106) as compared to when in the clamped position depicted in FIG. 1A.

This reduced amount of pressure and reduced height reduce the likelihood of stubbing and rolling over of the stack (106), but allow for movement of the incoming media sheet (102). Such a reduced height and pressure may be maintained during certain operations. For example, the media clamps (104) may remain in this intermediate position during an x-direction alignment of the incoming media sheet (102). In the present specification, an x-direction is perpendicular to the sheet transport direction (FIG. 1A, 112) or y-direction and may be into the page. After this x-direction alignment, the media clamps (104) may be lowered to the clamped position as depicted in FIG. 1A. When in the clamped position, or prior to returning to the clamped position, the incoming media sheet (102) may be aligned in a y-direction. If the media clamps (104) are not yet in the clamped position as the y-direction alignment begins, the media clamps (104) may be in the clamped position by the end of the y-direction alignment. While in the clamped position, the system (100) maintains alignment, and control, of the incoming media sheet (102) relative to the stack (106) and prepares for the reception of a new incoming media sheet (102).

The system (100) described herein includes media clamps (104) movable between multiple positions or heights allowing for enhanced finishing by addressing the difficulties in finishing undried or partially-dried incoming media sheets (102). More specifically, the media clamps (104) allow for accommodating undried or partially-dried incoming media sheets (102) that may have a greater propensity for misalignment and that exhibit page curl, which page curl may interrupt the media transport. While specific reference is made to the system (100) operating on partially-dried media, the system (100) may also be implemented to receive fully-dried media.

FIG. 2 is a flowchart of a method (200) for preventing media misalignment during accumulation, according to one example of the principles described herein. According to the method (200), media clamps (FIG. 1, 104) having multiple positions are placed (block 201) into a clamped position until a leading edge of the incoming media sheet (FIG. 1, 102) has passed over a trailing edge (FIG. 1, 108) of the stack region (FIG. 1, 114). In other words, before the incoming media sheet (FIG. 1, 102) is to be deposited on the stack (FIG. 1, 106), the media clamps (FIG. 1, 104) are in a down, or clamped, position. This position is indicated in FIG. 1A. In the clamped position the media clamps (FIG. 1, 104) maintain an x-direction alignment, a y-direction alignment, and z-axis rotational alignment of the stack (FIG. 1, 106) of media. In other words, while in the clamped position, the sheets in the stack (106) are prevented from moving relative to one another and therefore are in proper alignment for subsequent operations or for movement to another section of the printing system. While in the clamped position, the media clamps (FIG. 1, 104) are also compressing air cushions that may be present between individual sheets in the stack (FIG. 1, 106). As described above, these air cushions reduce surface friction between adjacent sheets. As the friction serves to maintain an alignment of the stack (FIG. 1, 106), a reduction in the friction increases the likelihood of a misalignment.

Once the leading edge of the incoming media sheet (FIG. 1, 102) has passed over the trailing edge (FIG. 1, 108) of the stack region (FIG. 1, 114), the media clamps (FIG. 1, 104) are raised (block 202). In other words, after the leading edge of the incoming media sheet (FIG. 1, 102) has passed over the trailing edge (FIG. 1, 108), but before coming into contact with the media clamp (FIG. 1, 104), the media clamp (FIG. 1, 104) is moved out of the transport path of the incoming media sheet (FIG. 1, 102). In this raised position the media clamps (FIG. 1, 104) do not interfere with the continual transport of the incoming media sheet (FIG. 1, 102). As the media clamps (FIG. 1, 104) are raised after the leading edge has passed over the trailing edge (FIG. 1, 108), the leading edge of the incoming media sheet (FIG. 1, 102) has already passed over the curled portion of the existing sheet and therefore the curled portion of the page is less likely to impact the transport of the incoming media sheet (FIG. 1, 102).

Once the incoming media sheet (FIG. 1, 102) has passed by the media clamp (FIG. 1, 104) in a sheet transport direction (FIG. 1, 112), the media clamps (FIG. 1, 104) are lowered (block 203) to a clamped position to align the incoming media sheet (FIG. 1, 102) with the stack (FIG. 1, 106). This lowering (block 203) of the media clamps (FIG. 1, 104) to the clamped position may come after a number of other operations. For example, after raising (block 202) the media clamps (FIG. 1, 104) to a high raised position, the media clamps (FIG. 1, 104) may be lowered to an intermediate position during x-alignment, and then lowered (block 203) to the clamped position during a y-direction alignment.

In returning to the clamped position, the system (FIG. 1, 100) is prepared to begin another sheet reception cycle including raising the media clamps (FIG. 1, 104) upon arrival of a new incoming media sheet (FIG. 1, 102). Returning to the clamped position also maintains alignment of the stack (FIG. 1, 106) which now includes the just received media sheet (FIG. 1, 102).

The method as described herein may allow for incoming media sheet (FIG. 1, 102) alignment within a stack (FIG. 1, 106) while addressing the complications that arise from processing certain media types such as undried or partially-dried media. For example, the media clamps (FIG. 1, 104) by clamping previous to the arrival of an incoming media sheet (FIG. 1, 102) suppress the page curl of the stack (FIG. 1, 106) so as to not interfere with the transport of the incoming media sheet (FIG. 1, 102). Thus, the system (FIG. 1, 100) reduces the effects of page curl that are likely to occur when using a printing fluid and improves the execution of finishing operations on such undried or partially-dried media.

FIG. 3 is a top view of a printing system (100) for preventing media misalignment during accumulation, according to another example of the principles described herein. In some examples, the system (100) includes a number of sets of media clamps (104). The different sets of media clamps (104) correspond to different media sizes. For example, a first set of media clamps (104-1) may pertain to a first media size (316-1). Similarly, a second set, third set, and fourth set of media clamps (104-2, 104-3, 104-4) pertain to a second, third, and fourth media (316-2, 316-3, 316-4) size, respectively. As indicated in FIG. 3, a set of media clamps (104-1) may include multiple media clamps (104). Examples of different media sizes include letter/A4 in different orientations, legal, and ledger/A3. The different media clamps (104) in addition to supporting different media sizes also support different media orientations. For example, as depicted in FIG. 3, the first set of media clamps (104-1) may be used to manage the alignment of letter/A4 size media in a landscape orientation. The second set of media clamps (104-2) may be used to manage the alignment of letter/A4 size media in a portrait orientation. The third set of media clamps (104-3) may be used to manage the alignment of legal size media in a portrait orientation. The fourth set of media clamps (104-4) may be used to manage the alignment of ledger/A3 size media in a portrait direction.

Accordingly, each set of media clamps (104) can manage the alignment of an incoming media sheet (FIG. 1, 102) that corresponds to the size (316) and location of the media clamps (104). As described above managing the alignment includes placing the corresponding media clamps (104) in a clamped position until a leading edge of the media sheet (FIG. 1, 102) has passed over the stack region (FIG. 1, 114) of the media support device, being in a raised position after the leading edge of the incoming media sheet (FIG. 1, 102) has passed over a trailing edge (FIG. 1, 108) of the stack region (FIG. 1, 114), and returning to the clamped position after the leading edge of the incoming media sheet (FIG. 1, 102) has passed the corresponding media clamps (104) to align the incoming media sheet (FIG. 1, 102) relative to the stack region (FIG. 1, 114). Using multiple sets of media clamps (104) allows for the alignment of media sheets of varying size.

As described above, the media clamps (104) maintain the alignment of the media stack (FIG. 1, 106) and also prevent page curl in the media stack (FIG. 1, 106). In receiving different media sizes (316), different amounts of pressure may be exerted upon the media stack (FIG. 1, 106) in order to reduce page curl. Accordingly, depending upon the application, media clamps (104) may be weighted to exert a sufficient force on the media stack (FIGS. 1, 106) to 1) prevent page curl and 2) to maintain an x-direction and a y-direction alignment of the media stack (FIG. 1, 106).

Within a set of media clamps (104) each individual media clamp (104) may be individually controlled while moving down to the clamped position to allow equal contact of the media clamps (104) within a set on at least one of a media stack (FIG. 1, 106) and a media support assembly. Doing so allows both media clamps (104) within a set to rest on the stack (FIG. 1, 106). Having both media clamps (104) in a set resting on the media sheet (102) ensures one contact point for each media clamp (104) to prevent sheet movement, for example during a y-direction alignment.

In addition to the individual media clamps (104) being independently controlled each of the sets of media clamps (104) are also independently controlled. For example, FIG. 4 is a side view of the printing system (100) of FIG. 3, according to one example of the principles described herein. In the example of FIG. 4, the stack (106) can include media sheets of any size (316). When the media size (316-1) corresponds to a particular set of media clamps (104-1), that set of media clamps (104-1) is activated to manage the alignment of any incoming media sheets (FIG. 1, 102) of the corresponding size (316-1). By comparison, when an incoming media sheet (FIG. 1, 102) is not of a corresponding media size (316-2, 316-3, 316-4); the corresponding media clamps (104-2, 104-3, 104-4) are in a raised position. As the media clamps (104) move between positions, the system (100) also includes a component that actuates, or engages the media clamps (104). In some examples, the media clamps (104) are actuated by motors that are coupled to the media clamps (104). In other examples, the media clamps (104) are actuated by motion of a media transport assembly.

FIG. 5 is a flowchart of a method (500) for preventing media misalignment during accumulation, according to another example of the principles described herein. According to the method (500) an intermediate position of the media clamps (FIG. 1, 104) is calibrated (block 501). Calibrating (block 501) the intermediate position of the media clamps (FIG. 1, 104) allows for a desired intermediate height to be set that does not interfere with the motion of the incoming media sheet (FIG. 1, 102) but that exerts some pressure during x-direction alignment and prevents some page curl. During manufacturing process, the manufacturing tolerances may not be tight enough to ensure a proper intermediate height that does not interfere with the transport path of incoming media sheets (FIG. 1, 102). Accordingly, calibrating the intermediate position ensures the desired intermediate height is set for the media clamps (FIG. 1, 104). More detail regarding the intermediate position calibration is given below in connection with FIGS. 7A-7E.

The method (500) also includes receiving (block 502) at least a partially-dry incoming media sheet (FIG. 1, 102). For example, the system (FIG. 1, 100) may receive an undried media sheet or a partially-dried media sheet. The undried or partially-dry incoming media sheet (FIG. 1, 102) may have curl in any direction such as an upward curl or a downward curl. As described above previous systems may dry the incoming media sheet (FIG. 1, 102) completely before performing any finishing operation. However so doing may elongate the length of time to receive a finished output as well as increasing the cost, size and complexity of the system (FIG. 1, 100). Accordingly, the method (500) includes receiving (block 502) an undried or partially-dry incoming media sheet (FIG. 1, 102) and performing certain operations to manage the alignment of such undried or partially-dried media sheets. As used in the present specification a partially-dried media sheet may be a media sheet that is sufficiently dry so as to not smear or smudge, but still contains printing fluid in a liquid form on the surface of or within the media sheet.

The media clamps (FIG. 1, 104) are placed (block 503) in a clamped position until a leading edge of the incoming media sheet (FIG. 1, 102) passes over a trailing edge (FIG. 1, 108) of the stack region (FIG. 1, 114). This may be performed as described above in connection with FIG. 2. The media clamps (FIG. 1, 104) are then raised (block 504) after a leading edge of the incoming media sheet (FIG. 1, 102) has passed over a trailing edge (FIG. 1, 108) of the stack region (FIG. 1, 114). This may be performed as described in connection with FIG. 2.

The media clamps (FIG. 1, 104) are then lowered (block 505) to an intermediate position during a remaining transport and an x-direction alignment of the incoming media sheet (FIG. 1, 102). For example, as depicted in at least FIGS. 1A-1C, the x-direction may be perpendicular to the media transport direction (FIG. 1, 112). Accordingly, the system (FIG. 1, 100) may include a component that aligns the media sheets in a direction perpendicular to the media transport direction (FIG. 1, 112) such that the media sheets are properly aligned. The media clamps (FIG. 1, 104) may be in an intermediate position to reduce the likelihood of stubbing and rolling over of the stack and offer an amount of resistance, but not so much as to impede the x-direction alignment of the incoming media sheet (FIG. 1, 102). For example, as described above, higher friction may be beneficial to maintain the alignment of the stack (FIG. 1, 106), but too high a friction may impede certain alignment processes. Accordingly, while in an intermediate position, the media clamps (FIG. 1, 104) maintain the alignment of the incoming media sheet (FIG. 1, 102) without providing such a high friction as to impede the x-direction alignment.

During a y-direction alignment of the incoming media sheet (FIG. 1, 102), the media clamps (FIG. 1, 104) are lowered (block 506) to a clamped position. In some examples, the media clamps (FIG. 1, 104) may be kept in the intermediate position until after the y-direction alignment has started, but are lowered before the y-direction alignment is completed. Doing so may prevent misalignment of the incoming media sheet (FIG. 1, 102) due to the y-direction alignment process. For example, FIG. 6 is a side view of a media clamp (104) for preventing media misalignment during accumulation, according to one example of the principles described herein. In this example, the y-direction alignment occurs as a media transport assembly causes the incoming media sheet (102) to contact a y-direction alignment wall (614) which aligns the stack (106) in the y-direction. However, due to the kinetic energy of the incoming media sheet (102) as imparted by the media transport assembly, the incoming media sheet (102) may rebound off the y-alignment wall (614) which may cause misalignment of the incoming media sheet (102) in the y-direction, or may cause an additional curl (110-3) at a portion of the incoming media sheet (102) that contacts the y-alignment wall (614) as indicated by the dashed line. Accordingly, by lowering the media clamp (104) into the clamped position during y-alignment as depicted in FIG. 6, the pressure of the media clamp (104) prevents the rebound back of the incoming media sheet (102) and hinders the creation of curl (110-3) at the alignment wall (614).

Returning to FIG. 5, Table (1) below provides the positioning of the media clamps (FIG. 1, 104) at different stages of a finishing operation as described, in part, in connection with FIG. 5. In this example, the incoming media size (FIG. 3, 316) is a Letter/A4 sized media sheet in a landscape orientation. In other words, just the media clamps (FIG. 3, 104-1) pertaining to the landscape/A4 landscape orientation size (FIG. 3, 316-1) media sheet are activated and all others are in a raised position.

TABLE 1 Incoming Media Sheet Position Media Clamp Position Incoming sheet (FIG. 1, 102) not over Down the stack region (FIG. 1, 106) until just over the trailing edge (FIG. 1, 108). Leading edge of the incoming sheet Up (FIG. 1, 102) passed over the trailing edge (FIG. 1, 108) of the stack region (FIG. 1, 106). Incoming sheet (FIG. 1, 102) past the Intermediate media clamp (FIG. 1, 104). x-direction alignment of the incoming Intermediate sheet (FIG. 1, 102). y-direction alignment of the incoming May be a combination of both sheet (FIG. 1, 102). Intermediate and Down Subsequent finishing operations Up Moving to other section of printing device Up

FIGS. 7A-7E are diagrams of the method for calibrating a media clamp (104), according to one example of the principles described herein. First, as depicted in FIG. 7A, the media clamp (104) is lowered to an elevation that is lower than a media support device (718). In this example, the media clamp (104) is positioned to the side of the media support device (718) as depicted in FIG. 7B.

Next, as depicted in FIG. 7B, the media support device (718) is moved, or translated towards the media clamp (104) as indicated by the arrow (720). A component of the system (FIG. 1, 100) then determines if there is contact between the media support device (718) and the media clamp (104). For example, when the media clamp (104) is lower than the media support device (718) as depicted in FIG. 1A, a translation of the media support device (718) would cause the media support device (718) to impact the media clamp (104). Such a contact results in a spike in the motor torque that moves the media support device providing detection of the contact.

If contact is detected, the media clamp (104) is then incrementally raised as indicated in FIG. 7C and the media support device (718) is again translated towards the media clamp (104) as indicated in FIG. 7B. In the setting depicted in FIG. 7C, contact would be detected and the media clamp (104) would again be raised in an incremental fashion to a position as indicated in FIG. 7D which would indicate no contact between the media clamp (104) and the media support device (718). Once no contact is detected between the media support device (718) and the media clamp (104), the intermediate position is set as an additional predetermined distance from the point of no contact as depicted in FIG. 7E. The operation depicted in FIGS. 7A-7E may be performed for all the media clamps (104).

FIG. 8 is a diagram of a media clamp (104), according to another example of the principles described herein. In this example, the media clamp (104) may be designed so as to align and exert pressure on the trailing edge (108) of the stack (106), not just proximate to the trailing edge (108). Doing so may further reduce the page curl and reduce the impact of any page curl on the transport of the incoming media sheet (102). Still further, the media clamp (104), or other media clamps (104) may be sized or placed to exert pressure over desired locations and area sizes of the stack (106).

Certain examples of the present disclosure are directed to systems and methods for preventing misalignment of an incoming media sheet that 1) prevents page jams; 2) prevents page defects such as bent or rolled edges or corners: 3) accommodates finishing for undried or partially-dried incoming media sheets; 4) maintains page alignment in a media support device; 5) simplifies post-printing operations; and 6) addresses page curl and cockle as well as alignment for a variety of media sizes. However, it is contemplated that the devices and methods disclosed herein may prove useful in addressing other deficiencies in a number of technical areas. Therefore the systems and devices disclosed herein should not be construed as addressing just the particular elements or deficiencies discussed herein.

The preceding description has been presented to illustrate and describe examples of the principles described. This description is not intended to be exhaustive or to limit these principles to any precise form disclosed. Many modifications and variations are possible in light of the above teaching. 

What is claimed is:
 1. A system for preventing media misalignment during accumulation, the system comprising: a number of media clamps having multiple positions to prevent misalignment of an incoming media sheet during accumulation, wherein the number of media clamps: are in a raised position after a leading edge of the incoming media sheet has passed over a trailing edge of the stack region; and are in a clamped position after the leading edge of the incoming media sheet has passed the number of media clamps.
 2. The system of claim 1, wherein the number of media clamps are proximate the trailing edge of the stack region.
 3. The system of claim 1, wherein the number of media clamps form a set selected from a number of sets of media claims, each set pertaining to a different media size.
 4. The system of claim 1, wherein: a raised position comprises an intermediate position and a high position; the number of media clamps are in the high position after the leading edge of the incoming media sheet has passed over the trailing edge of the stack region; and the number of media clamps are in the intermediate position during an x-direction alignment of the incoming media sheet.
 5. The system of claim 4, wherein the number of media clamps are in the intermediate position for a portion of a y-direction alignment of the incoming media sheet.
 6. The system of claim 1, wherein the number of media clamps are in a clamped position until a leading edge of the incoming media sheet has passed over the trailing edge of the stack region.
 7. A method for preventing misalignment of an incoming media sheet, the method comprising: placing media clamps having multiple positions in a clamped position until a leading edge of the incoming media sheet has passed over a trailing edge of a stack region; raising the media clamps after the leading edge of the incoming media sheet has passed over the trailing edge of the stack region; and lowering the media clamps to align the incoming media sheet with the stack region after the leading edge of the incoming media sheet has passed the media clamp.
 8. The method of claim 7, further comprising: lowering the media clamps to an intermediate position during an x-direction alignment of the incoming media sheet; and lowering the media clamps to a clamped position for at least a portion of a y-direction alignment of the incoming media sheet.
 9. The method of claim 7, wherein raising the media clamps comprises raising the media clamps to a high position after the leading edge of the incoming media sheet has passed over the trailing edge of the stack region.
 10. The method of claim 7, further comprising receiving at least a partially-dry incoming media sheet.
 11. The method of claim 7, further comprising calibrating an intermediate height of a set of media clamps relative to a media support device by: lowering the media clamps to an elevation lower than the media support device; translating the media support device towards the media clamps; detecting contact between the media support device and the media clamps; incrementally raising the media clamp and translating the media support device towards the media clamps until no contact is detected between the media support device and the media clamps; and once no contact is detected between the media support device and the media clamps, raising the media clamps a predetermined distance.
 12. A system for preventing misalignment of an incoming media sheet, the system comprising: a number of sets of media clamps having multiple positions, each set of media clamps corresponding to a different media size, each set to: manage alignment of an incoming media sheet when the incoming media sheet is of a corresponding media size, wherein when managing alignment of an incoming media sheet, a set of media clamps: are in a clamped position until a leading edge of the incoming media sheet has passed over a stack region of a media support device; are in a raised position after the leading edge of the incoming media sheet has passed over a trailing edge of the stack region; and return to the clamped position to maintain an alignment of the incoming media sheet relative to the stack region; and be in a raised position when an incoming media sheet is not of a corresponding media size.
 13. The system of claim 12, wherein a set of media clamps are aligned with the stack region of a corresponding media size.
 14. The system of claim 12, wherein motion of media clamps within a set is independently controlled to allow equal contact of the media clamps within the set on at least one of a media stack and media support assembly.
 15. The system of claim 12, wherein at least one set of media clamps is actuated by motion of a media transport assembly. 